Pre-rounding element on a rounding apparatus

ABSTRACT

When rounding metal sheet sections for forming can bodies by means of a rounding machine, a pre-rounding element is used, whose lower part is deflectable with respect to the upper part by means of an actuating element. Thereby, the joint between the upper and the lower part is executed as a solid body joint whose section modulus in bending during the deflection is different along the joint. Thereby, a uniform impact on the metal sheet may be reached. Furthermore, the separating gap between the upper and the lower part is arranged obliquely, thus reducing the bending of the lower part.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional Application of U.S. application Ser.No. 12/630,962, filed Dec. 4, 2009 and claims the benefit of Swisspatent application 1929/08, filed Dec. 9, 2008, the disclosures of whichare incorporated herein by reference in their entirety.

BACKGROUND

The invention is related to a pre-rounding element or a rounding elementin a rounding apparatus, a rounding apparatus with such a pre-roundingelement or a rounding element, as well as a welding device for canbodies with such a rounding apparatus.

PRIOR ART

Rounding apparatuses are used in the manufacturing of container bodies,particularly can bodies, made of metal sheet. For this, after therounding, the container body blanks are transported directly into awelding machine for the welding of the longitudinal seam of the body.Thereby, the destacking of the metal sheets, the rounding apparatus andthe welding machine normally form an entity. Corresponding systems forthe production of cans are for example known from DE-A-33 30 171 or fromU.S. Pat. No. 5,209,625. Thereby, the rounding takes place in such away, that the formed can body can be guided directly into the Z-railused for the seam overlapping. For the rounding, the metal sheetsections which are cut rectangularly, with defined dimensions andmaterial characteristics recorded in standards, are pushed by a dispatchsystem into a first actuated transport roller pair, transported furtherby multiple actuated transport rollers with a speed of 100-450 m/min.and bent to a round body in a rounding apparatus with a rounding system,by means of wedges and rollers or by means of roller systems.Particularly, a pre-rounding wedge located ahead of the rounding rollersis used, influencing the rounding result. Optionally, a preliminaryplastic deformation serving for stress relief in the metal sheet beforethe rounding additionally takes place in advance, by means of a wedgesystem of an optional flexer station. Such rounding apparatuses orinstallations respectively are known to the skilled person. Depending onthe quality of the metal sheet, the metal sheets produced in series havedifferent sheet thicknesses and material characteristics, like yieldpoint, elongation and strength characteristics, which lead to differentbody diameters after the rounding process and therefore to differentopenings at the free ends. Because thereby not all of the frames roundedin series are located at the same position within the rounding stationand they have different rounding diameters, this may result invariations of the degree of overlapping in the welding station, which isproblematic for the welding of the body, or it may lead to problemsduring the lateral pushing of the bodies out of the rounding machine andinto the welding installation and therefore to a machine stop with longdowntimes. The efficiency of the machine is thereby reduced andshortfall costs arise for the machine operator.

According to the prior art, the adjustment of the pre-rounding wedge isdone manually and it depends on the mentioned metal sheetcharacteristics, like yield point, metal sheet thickness and also on theformat dimensions of the metal sheets. If different metal sheetqualities have to be handled, the pre-rounding wedge has to be adjustedevery time again during the idle time of the rounding apparatus. Inorder to avoid said problems when rounding and welding can bodies, metalsheets with low variations in material characteristics and from onemanufacturing series of the metal sheet producer are used. A mixing ofdifferent metal sheets is avoided as much as possible. The rounding hasto be often checked and the rounding system, particularly thepre-rounding wedge, has to be readjusted if necessary, wherein this hasto be done during the idle time, thus resulting in a lower efficiency ofthe rounding apparatus and of subsequent steps and in shortfall costsfor the machine operator. During operation, the adjusted pre-rounding orrounding by means of the pre-rounding element and/or of the roundingelement may vary depending on the different force which the metal sheetsexercise on the element. A pre-rounding element with an actuatingmember, apt for avoiding these disadvantages, is proposed in the Swisspatent application No 0608/08.

SUMMARY OF THE INVENTION

It is the task of the invention to improve such a pre-rounding elementor rounding element.

This is achieved by a pre-rounding element or a rounding element in arounding apparatus, comprising a substantially rigid upper element partwhich is formed to be attached at the rounding apparatus by means ofattachment members, or which is formed by an apparatus-fixed part of therounding apparatus, a lower element part designed for acting upon themetal sheets to be rounded, which are located in the rounding apparatus,a joint arrangement by means of which the lower element part isconnected to the upper element part in an articulated way, as well as atleast an actuating element by means of which the lower element part isdeflectable in such a way, that metal sheets to be rounded can beactuated differently by the lower element part, wherein the jointarrangement has a solid body joint which connects the upper element partand the lower element part in a substantially continuous way and whichhas areas, along its longitudinal elongation, with different sectionmodulus's in bending for the deflection movement particularly areas ofdifferent material thickness, wherein the section modulus in bending orthe material thickness respectively has its highest value in the areawhere the actuating element introduces a force which acts on the lowerelement part. The task is further achieved by a pre-rounding element ora rounding element in a rounding apparatus, comprising a substantiallyrigid upper element part which is formed to be attached at the roundingapparatus by means of attachment members, or which is formed by anapparatus-fixed part of the rounding apparatus, a lower element partdesigned for acting upon the metal sheets to be rounded, which arelocated in the rounding apparatus, a joint arrangement by means of whichthe lower element part is connected to the upper element part in anarticulated way, as well as at least an actuating element by means ofwhich the lower element part is deflectable in such a way, that metalsheets to be rounded can be actuated differently by the lower elementpart, wherein the separating gap between the upper element part and thelower element part, which follows the joint of the joint arrangement,runs with a deviation from the horizontal direction and the end ofseparating gap, located opposite of the joint, is located above thejoint with respect to the horizontal direction.

This permits a change of the impact of the metal sheet to be roundedduring operation and at the same time keeps the adjusted influence onthe metal sheet constant.

The pre-rounding element or rounding element has a solid body joint,thus resulting in a simple construction. The solid body joint works in aplay-free and wear-free way. Thereby, the solid body joint is formed insuch a way, that a mostly uniform deflection by the actuating memberresults. This results in a uniform influence of the element on the metalsheet and therefore in a good and uniform rounding result.

According to a further aspect of the invention, the pre-rounding elementor the rounding element is constructed by means of the claimed featuresin such a way, that its lower part is deformed as little as possibleduring its influence on the metal sheet. This results in a more uniforminfluence of the element on the metal sheet and therefore in a good anduniform rounding result.

Such a pre-rounding element and/or rounding element are used in arounding apparatus and in a welding device according to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Further embodiments, advantages and applications of the invention resultfrom the dependent claims and from the now following description bymeans of the figures.

FIG. 1 is a side view of a pre-rounding element for a generalexplanation of its construction;

FIG. 2 schematically shows the arrangement of a pre-rounding elementaccording to the invention in a rounding apparatus;

FIG. 3 is a graphical view of an embodiment of a pre-rounding element;

FIG. 4 is a side view of the pre-rounding element of FIG. 3;

FIG. 5 is a vertical view of the pre-rounding element of FIG. 3 or FIG.4 respectively;

FIG. 6 is a backside view of a pre-rounding element;

FIG. 7 is a side view of part of a further embodiment of a pre-roundingelement; and

FIG. 8 is a horizontal section view through the embodiment according toFIG. 7.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows in a side view a pre-rounding element 14. Its operationwithin a rounding apparatus 4 is shown schematically in FIG. 2. Therounding element 13 of the rounding apparatus 4 may be executedaccording to the aspects of the invention as well. In the followingexamples they will be explained by means of a pre-rounding element,however the corresponding execution and use as rounding element isincluded therein as well.

The pre-rounding element 14, which is a pre-rounding wedge in the shownembodiment, because its lower part 22 which acts upon the respectivemetal sheet is wedge-shaped in its front section, has a rigid or, duringoperation, fixed upper element part 20 respectively. In this embodiment,it is a part 20 which is executed to be fixed at a machine part of therounding apparatus, in the shown example having attachment means on bothsides, for example bores 26 and guides 24, which allow an attachment tothe rounding apparatus and a vertical base setting to it. The upper part20 which is apparatus-fixed at the rounding apparatus may also directlybe a fix part of the rounding apparatus. An alternative attachment maybe carried out by means of vertical threaded rods for the adjustment ofthe height and at least a vertical guide and a final fixing by means ofat least a horizontal screw which pulls the part 20 against the verticalguide.

The deflectable lower element part 22 or the lower wedge part 22respectively is arranged at the part 20 or at the upper element partrespectively, by means of a joint arrangement 21. The deflection isshown by means of an arrow a. The deflection is made possible by anactuating element 23 which will be called actuator in the following. Theactuator is firmly arranged with its stationary part in the upper part20 and the movable, actionable part 23′ of the actuator acts upon thelower part of the wedge 22; alternatively, the movable part is fixed inof the upper part and the other part of the actuator acts upon the lowerpart of the wedge. If the part 23′ presses downwards in the figure, thelower wedge part 22 is deflected in such a way, that it can take on theposition which is drawn punctuated position in case of a maximumdeflection. If the actionable part 23′ of the actuator 23 is in astationary position, the position of the wedge 22 shown with a solidline is reached. Depending on the force or on the deflection beingexerted by the actuator on the wedge 22, a preliminary position betweenthe shown positions results. The actuator may pull the part 22 upwardsas well. Then, a middle position between both of the shown positions mayfor example be the non-deflected position.

The joint arrangement connecting the upper part 20 and the wedge 22 is asolid body arrangement in this example, consisting of a suitablydimensioned solid body joint which is elastically deformed by the forceof the actuator 23. Accordingly, a retraction is the result when theforce of the actuator or its deflection is reduced. The restoring forcemay also be generated by the actuator. Preferably, the joint arrangement21 is executed as a solid body joint in one piece with the upper part 20and the lower part 22, as shown in FIG. 1. The actuator 23 may be anarbitrary controllable drive. A piezo-electrical actuator is preferredbecause small deflections only are necessary and a fast reaction time isadvantageous. Other controllable drives may also be used as an actuatingelement 23, like electromotive drives, magnetic drives, a pneumaticdrive or a hydraulic drive.

FIG. 2 shows schematically the feeding of a metal sheet 1 into arounding apparatus 4, inside of which a further metal sheet 2 is alreadyin the rounding process. The metal sheets have been destacked from astack not shown here and are continuously rounded by the roundingapparatus. The feeding into the rounding apparatus is done my means of atransport, for example by means of the shown rollers. A flexer stationwith flexer rollers 8 and 9 and a flexer wedge 7 may be provided withinthe rounding apparatus. Such flexer stations are known; on one side theyremove tensions from the metal sheet and on the other side they cause arounding of the front edge area of the respective metal sheet.Particularly, a measurement installation used for example for measuringthe rounding characteristics of the respective metal sheet, which willbe explained in the following, may be connected to the flexer station ormay be a part of the latter respectively. Following the flexer station,the actual rounding station of the rounding apparatus 4 is shownschematically. It has the rounding rollers 11 and 12 and a roundingwedge 13 following it in transport direction. These elements arebasically known and will not be explained here in more detail. Adifferent type of rounding station may be used instead of such arounding station, for example a rounding station without a wedge andwith shifted rollers. This type is known to the skilled person and willnot be explained here.

The pre-rounding element 14 according to the invention is arranged aheadof the rounding rollers and impacts the metal sheet to be rounded.According to the invention, this is done by means of the lower elementpart 22, which is deflectable during the rounding operation. Thereby,during the rounding it may be acted individually upon each metal sheetby means of the pre-rounding element 14 and the rounding result may beinfluenced for each metal sheet. Thereby, the actuator 23 is controlledby a signal coming from a controller 5. This may be the controller ofthe rounding apparatus or the controller of a welding device forcontainer bodies comprising the rounding apparatus. The controller 5 mayalso be a separate controller which interacts with said controllers ifnecessary. Thereby, the controlling of the pre-rounding element 14 forexample takes place in the meaning of a pre-setting of the roundingapparatus by an operator, such that the operator prescribes a certaindeflection of the lower part 22 by means of the controller 5. Followingthis, it is stuck to the pre-setting for all metal sheets until theoperator sets a new pre-setting. On the other side, the deflection maybe chosen from recorded default values by the controller 5. The operatorthen inputs for example the metal sheet format and/or the metal sheetmaterial and/or the metal sheet thickness and/or a code label and thecontroller chooses the corresponding deflection of the lower elementpart 22 from the recorded values. In a preferred embodiment, themeasurement of at least a metal sheet characteristic is done by means ofat least a measurement installation 27 and the measured value triggersthe controller 5 to adjust the actuator 23 or the deflection of thelower element part 22 respectively. The measurement may preferably bedone for each metal sheet and thereby the pre-rounding element may beadjusted or controlled respectively for each metal sheet of the sequenceof metal sheets to be rounded. However, the measurement may be carriedout for individual metal sheets only, for example for each tenth metalsheet or for only one metal sheet of a lot of metal sheets, for examplethe first metal sheet of a metal sheet stack. The metal sheet thicknessmay for example be used as measuring value. Such installations are knownand will not be explained here in more detail. Preferably, the roundingbehaviour of the metal sheet is measured and used for controlling thepre-rounding element 14, this being explained in more detail in thefollowing.

FIGS. 3 to 6 show an embodiment of an element 14, featuring both aspectsof the invention. On one side, the joint 21 is executed in such a way,that its section modulus against the deflection is different along itslongitudinal elongation. On the other side, the separating gap 21′between the upper part 20 and the lower part 22 is not executedfollowing a horizontal direction (thus not as shown in FIG. 1) and theopening of the separating gap 21′ located opposite of the joint liesabove the joint 21. These aspects will be explained in more detail inthe following.

The graphical view of the pre-rounding element 14 shows this elementwith the upper part 20 and the lower part 22, which are connected bymeans of the joint 21. The latter is a solid body joint which may beexecuted by a one piece construction of the upper part 20 and the lowerpart 22 in this example. The solid body joint may also be executed inanother way, for example by means of a leaf spring arrangement. The onepiece execution is at most related only to the connection between theupper part 20 and the lower part 22. The lower part 22 itself may beexecuted from multiple parts, particularly the actual wedge tip 22′ ofthe pre-rounding element 14 may consist of a different material that thelower part 22. Thereby, a more wear resistant and stronger material thanfor the lower part 22 may particularly be chosen for the wedge tip 22′.The connection of the parts 22 and 22′ may be carried out by welding,bonding or in another way. Within a preferred embodiment, the back partof the wedge and the front part are screwed together, thus allowing thereplacement of the front part, either because of wear or for changingthe shape of the wedge. The already mentioned side guides 24 and 24′ ofthe element 4 and the bores 26, particularly threaded bores, for thevertical fixing of the element 14 to the rounding machine are shown inFIG. 3; as explained, another type of connection may be used as well.The actuating element 23 is not shown in FIGS. 3, 4 and 5. In thisembodiment, it is designed in such a way, that it is attached to the topof the upper part 20 by means of threaded bores 17, such that the tappet23′, which is indicated in FIG. 1, is guided through the cavity or theguide 19 respectively and downwards towards the lower part 22. Ahorizontal threaded bore 18, which may be arranged on the front side, asshown in FIG. 3, or on the back side, as shown in FIG. 5, serves for theinsertion of a threaded bolt which itself may serve for the alignment ofthe tappet 23′. The tappet of the actuator may also be guided in anothermanner. A support 23″ for the actuator, itself not depicted in thefigure, is shown in FIG. 6 above the upper part 20.

FIG. 3 shows the one end of the solid body joint 21. This joint ispreferably arranged without interruption across the entire length of thepre-rounding element 14. If necessary, the joint may also haveinterruptions. In FIG. 3 and particularly in FIG. 4, the latter showinga top view of the side of the element 14 with the guide 24 seen in FIG.3, it is shown that the material thickness of the joint 21 is small atits end. This is shown in the side view of FIG. 4 by the small materialthickness labelled with the numeral 54. On the contrary, FIG. 5 shows avertical section through the middle of the element 14 and thereforethrough the guide 19, wherein it is evident that the material thickness54 of the joint is higher over there. The material thickness of thejoint 21 decreases towards the other lateral end with the guide 24′,until it is as low as shown in FIG. 4 also at this lateral end. Withinthis pre-rounding element 14, for which the introduction of force takesplace through the middle by means of the actuating element, this being apreferred embodiment, a more uniform deflection of the lower part 22across the entire length of the pre-rounding element is reached by meansof the material thickness of the joint when bent by the actuator, whichdecreases starting from the middle in a lateral direction to theoutside, as this would be the case without this measure. This results ina more uniform impact of the lower part 22 on the metal sheet to berounded and thereby in an improved rounding result. FIG. 5 shows theintroduction of force, wherein the force F which is initiated by theactuating element causes the deflection a of the lower part 22.Regarding the choice of the material thickness, the joint 21 is executedat the position of the pre-rounding element 14, whereat the introductionof force occurs by means of the actuating element, in such a way that atthat position the bending resistance element is the highest and it isreduced with an increasing distance from the position of introduction offorce. This may be done in the shown way by reducing the materialthickness or the cross section of the joint respectively with increasingdistance from the position of introduction of force. This may also bedone by means of a change of another material parameter of the solidbody joint, for example by means of an execution of the solid body jointin sections of different materials which have a different sectionmodulus in bending.

The execution of the change of the material thickness may for example bedone starting from the outside of the element 14, as shown in theembodiments of FIGS. 3 to 6. There it is seen that the materialthickness of the solid body joint decreases starting from the middleposition of introduction of force of this embodiment in such a way, thatat least a material removal 51 reducing the material thickness of thesolid body joint towards both sides takes place on the rear of the outerside. Preferably, further removals 52 and 53 are carried out such that afaceted removal of material on the rear side results. A change ofmaterial thickness on the outer sides results as well if the solid bodyjoint is formed by a leaf spring package which has more leaf springs atthe position of introduction of force than towards the sides of theelement 14. The different material thickness 54 may also be executed bymeans of different diameters of a cavity 21″, particularly a bore,defining the solid body joint; another type of processing like forexample milling may be used instead of a bore process. The provision ofsuch a cavity is shown in FIGS. 7 and 8, wherein only the joint part ofthe pre-rounding element 14 is shown. Thereby, a section of the upperpart 20 and a section of the lower part 22 are shown in side view inFIG. 7 and it is evident that the cavity 21″, particularly the bore,defining the joint 21, is a stepwise cavity or stepwise borerespectively. This is shown in FIG. 8 in the horizontal section view atthe cutting line A-A of FIG. 7. It shows a section of the lower part 22and the bore 21″ of the joint, which has a smaller diameter in sectionstowards the middle of the joint. Thereby, the material thickness of thesolid body joint increases towards the middle or decreases towards theouter sides respectively. Instead of a stepped bore a tapered shape ofthe bore may be provided as well. The cavity may also be executed inanother manner, for example by means of a slit with a radius at oneside.

The shown examples assume a centred introduction of force and hence areduced section modulus in bending towards the outer sides of theelement 14. This may be executed in a different way as well, byintroducing the force on both outer sides and thereby providing thesection modulus in bending or the higher material thickness respectivelyat the outer parts. The material thickness would then decrease towardsthe middle. In the examples, the joint is also placed at the rear sideof the element 14; this is however not mandatory, the joint may bearranged at the front side of the element 14 or in its middle or inother intermediate positions between the rear side and the front side aswell.

FIGS. 3 to 6 show the second aspect of the invention, according to whichthe separating gap 21′ between the upper part 20 and the lower part 22runs differently than in the horizontal direction. As already mentioned,the force F of the actuating element acts upon the lower part 22.Furthermore, during the rounding process, the resisting force F_(Blech)acts upon the lower part 22. These two forces cause a deformation of thelower part, particularly of the edge of the wedge tip 22′. The lowerpart 22 of the element 14 has a higher volume and thereby a highersection modulus in bending against the bending of the edge 22′ becauseof the course of the separating gap 21′ which deviates from thehorizontal direction. A better rounding result is reached because of areduction of this bending. The separating gap 21′ preferably runsoblique to the horizontal direction and particularly straight, thusresulting in an easy manufacturing. Thereby, the deviation from thehorizontal position can be seen in case that the element 14 is built-inas required or in case of the element which is held in its mountingposition by means of attachment members respectively. It is furtherpreferred that the surface 55 of the element 22 facing the roundingroller 11 of the rounding apparatus 4 has a concave rounded andparticularly substantially cylinder-envelope-shaped section. This shapealso has an influence of reducing the bending. Instead of a rounding,multiple oblique and uniform surfaces, which substantially equal arounding, may be provided.

1. A pre-rounding element or a rounding element in a rounding apparatuscomprising: a substantially rigid upper element part which is formed tobe attached at the rounding apparatus by means of attachment members, orwhich is formed by an apparatus-fixed part of the rounding apparatus, alower element part designed for acting upon the metal sheets to berounded, which are located in the rounding apparatus, a jointarrangement by means of which the lower element part is connected to theupper element part in an articulated way, as well as at least anactuating element by means of which the lower element part isdeflectable in such a way that metal sheets to be rounded can beactuated differently by the lower element part, wherein the jointarrangement includes a solid body joint between the upper element partand the lower element part and a separating gap extending from the solidbody joint such that an end of the separating gap is located opposite ofthe solid body joint and above the joint with respect to the horizontaldirection.
 2. The pre-rounding element or the rounding element of claim1, wherein the separating gap runs oblique to the horizontal direction.3. The pre-rounding element or the rounding element of claim 1, whereinthe surface of the element facing the rounding roller of the roundingapparatus has a section with a shape selected from the group consistingof concave, concave rounded and cylinder-envelope-shaped shape.
 4. Arounding apparatus for rounding individual metal sheets comprising thepre-rounding element or the rounding element of claim 1 and a controllerfor the actuation of the pre-rounding element depending on at least oneof an input value, a default value and a measured value of the metalsheet characteristic of individual metal sheets to be rounded.
 5. Awelding device for can bodies comprising: a Z-rail for positioning ofbody edges, welding rollers having intermediary wire electrodes runningthereon, and the rounding apparatus of claim 4.